Hedgehog (Hh) signaling has been implicated in the pathogenesis of several types of sarcomas. The goal of the proposed research is to develop drugs that block modification of Hh proteins with palmitate and thereby prevent Hh mediated growth of human sarcomas. In order to signal correctly, Hh must be modified by attachment of the 16-carbon fatty acid palmitate to its N-terminus. We aim to exploit Hh palmitoylation as a potential Achilles heel by targeting Hhat (Hedgehog acyltransferase), the enzyme that catalyzes attachment of palmitate to Hh. My laboratory developed an in vitro Hh palmitoylation assay that is dependent on Hhat activity. The assay was optimized for High Throughput Screening (HTS) to identify small molecule inhibitors of Hhat. We completed the HTS, identified multiple “hits”, and chose 4 lead compounds. Since palmitoylation is required for Hh function, Hhat inhibitors that block Hh palmitoylation could be developed into novel chemotherapeutics that will be efficacious in the treatment of sarcoma.
Aim 1) To determine the effect of Hhat and Hh depletion on sarcoma cell proliferation. Human sarcoma cells will be transduced with lentiviruses encoding ShRNAs directed against Shh, Dhh, Ihh or Hhat and the effects on cell proliferation, survival and migration will be determined.
Aim 2) To identify small molecule inhibitors of Hhat that inhibit proliferation of sarcoma cells in tissue culture and in animal models. We will assess the ability of selected Hhat inhibitors to inhibit proliferation, survival and migration of human sarcoma cell lines in vitro. Pharmacokinetics and pharmacodynamic parameters for the Hhat inhibitors will be determined in mice. The effects of Hhat inhibitors in a xenograft tumor model in vivo will then be assayed. The most effective inhibitors will be derivatized and assayed for further therapeutic development.